Refrigerating apparatus



Jan. 4, 1944. R. E. GOULD 2,338,240

REFRIGERATING APPARATUS Filed April 23, 1942 V 3 Sheets-Sheet 1 W t M INVENTOR.

Jan. 4, 1944. R. E. GOULD REFRIGERATING APPARATUS Filed April 23, 1942 3 Sheets-Sheet 2 Q1 pg a 22 1NVENTOR. v %,M 94

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HR. 1:. GOLJLD 2,338,240

Jan. 4, 1944.

REFRIGERATING APPARATUS 3 Sheets-Sheet 3 Filed ApI il 23, 1942 INVENTOR.

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Patented Jan. 4, 1944 REFRIGERATING APPARATUS Richard E. Gould, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application April 23, 1942, Serial No. 440,122

10 Claims.

This invention relates to refrigerating apparatus and more particularly to an improved arrangement for balancing the compressor capacity with the refrigeration requirements.

One object of this invention is to provide a simple and inexpensive unloading mechanism for a compressor.

Another object of this invention is to provide an improved control arrangement for unloading one or more cylinders of a multiple cylinder compressor.

Still another object of this invention is to provide an unloading mechanism carried wholly by the discharge valve plate of a compressor.

More particularly, it is an object of this inven tion to so construct and arrange the unloading mechanism that it may be added to a standard compressor merely by removing the standard valve plate and substituting a new valve plate provided with my improved compressor unloading mechanism.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 diagrammatically shows a refrigerating system incorporating my improved invention.

Fig, 2 is a fragmentary view of a portion of the compressor, with parts broken away, showing the means used for lifting one of the outlet valves.

Fig. 3 is a fragmentary sectional view taken substantially along the line 3-3 of Fig. 4.

Fig. 4 is a fragmentary sectional view taken on line 4-4 of Fig. 3.

Fig. 5 is an exploded view showing a number of the elements which make up the unloading means.

Fig. 6 is a plan view of the valve plate.

Referring now to Fig. l in which I have shown somewhat diagrammatically arefrigerating system embodying my invention, reference numeral [0 designates a four-cylinder compressor provided with a drive pulley l2 which is adapted to be driven by a motor, not shown. The compressed refrigerant leaves the compressor through the I line l4 which leads to the condenser It. For

purposes of illustration, I have shown a fan unit l8 for flowing air over the condenser so as to cause the .compressed refrigerant to condense. The condensed refrigerant is collected in the receiver 20 from whence it is supplied to the evaporator 22. The flow of liquid refrigerant to the evaporator 221s controlled by means of a thermostatic expansion valve 24. Air to be conditioned is circulated over the evaporator 22 by means of I a blower unit 26. The refrigerant vapor returns to the crank case of the compressor through the suction line 28 in accordance with conventional practice.

Since the load on a compressor varies considerably from time to time, it is desirable to provide some means forvarying the capacity of the compressor so as to avoid the need for frequently cycling the compressor. A large number of arrangements have been proposed for unloading one or more cylinders of a compressor, no one of which has proven fully satisfactory. Most of the prior art arrangements for unloading a multiple cylinder compressor include some means for holding open one or more of the suction valves, in response to suction pressure, whereas in my unloading arrangement I provide thermostatically controlled means for holding open one or more of the discharge valves.

As shown in Fig 1, I have provided a thermostat 31] which is preferably located so as to respond to the temperature of the air within the conditioned space. The thermostat 30 controls the circuit of a solenoid operated valve 32 located in a line 34 leading from the main suction line-28 to the discharge valve lifting mechanism carried by the valve plate 38.

For purposes of illustration, I have shown one valve plate 38 which serves two of the cylinders and a separate valve plate 40 which serves the other two cylinders. corresponding cylinder head 42 are secured to the main body 44 of the compressor by means of cap screws 46. The cylinder head element 48 and the corresponding valve plate 40 are similarly held in place by means of a corresponding set of cap screws 46. The valve plate 40 is provided with the usual form of discharge valves, not shown. While the number of cylinders provided with unloading means may be varied, I have shown an arrangement in which only two of the cylinders are unloaded.

As best shown in Fig. 3, the compressed refrigerant leaves the compression chamber 49 through a series of discharge ports 50 provided in the valve plate 38. The iiow of compressed refrigerant through the ports 50 is controlled by a ring shaped valve plate 52. A plurality of springs 54 bias the ring 52 into engagement with the upper surface of the valve plate 38 so as to normally prevent the return flow of compressed gas through the discharge ports 50 during the suction. stroke of the piston 56. Each of the four compressor pistons is provided with a conven- The valve plate 38 and its tional suction valve (not shown) in accordance with standard practice. The springs 54, as best shown in Fig. 5, are mounted in recesses 58 provided in the block 60. The block 60 is held in place by means of one or more cap screws 62.

A valve lifting piston 64 is slidably mounted within the recess 66 provided within the block Eli. A spring 68 normally biases the piston 84 into its lowermost position in which position it does not interfere with the normal operation of the ring shaped valve plate 52. The piston 64 carries a valve lifting element I which, for purposes of illustration, has been shown provided with five arms 12 which normally rest within the five recesses 14 cut into the upper surface of the valve plate 38. The block 60 is provided with a passage 15 which communicates with the passage 16 pro-=- vided in the valve plate 38. The passage it in turn communicates with the pipe line 34 in which the solenoid valve 32 is mounted. By virtue of the above described arrangement, openingof the valve 32 subjects the upper end of the piston (it to a pressure corresponding to the suction pressure or the low side pressure existing in the suction line 28. Inasmuch'as the lower end of the piston 64 is subjected to a pressure corresponding to the high side pressure, or in other words the pressure on the discharge side of the compressor, the piston 64 moves upwardly against the action of the spring 68 so as to cause the arms '12 to lift the valve ring 52 away from the discharge ports 50. Fig. 2 of the drawings shows the piston 54 in its lowermost position whereas Fig. 3 shows it in its uppermost position. The path of the compressed refrigerant leaving the compres sion chamber 56 is shown in Fig. 3 by means of the arrows.

Both of the discharge valves carried'by the valve plate 38 are provided with identical means for holding the discharge valvesopen in the man ner and for the purpose described hereinabove. Inasmuch as both valve lifting means are identical in construction and operation, only the one valve lifting means has been shown in detail in the drawings. Each of the valve lifting pistons 64 may be controlled by the same solenoid valve 32, but it is within the purview of this invention to provide a separate solenoid valve for controlling each of the valve lifting pistons and to provide separate thermostats for controlling each solenoid valveso that the discharge valves may be opened at different temperatures. However, in order to simplify this disclosure, only. one ther= mostatlcally controlled solenoid valve has been shown.

As best shown in Fig. 5, a cylindrical projec tion 18 has been provided on the lower side of the block 60. This projection serves to space the main portion of the block 60 from the upper side of the valve plate 38. Notches 80 have been pro vided in the projection 18 so as to provide clear ance for the valve lifting arm 12. A small cou pling element- 82 joins the passage 15 provided in the block 60 with the passage 16 provided in the valve plate 38. By virtue of the above described arrangement, it is apparent that all of the compressor unloading mechanism is directly supported on the valve plate 38, This construction not only simplifies the manufacture and assembly of the unloading mechanism but also makes it possible to equip standard compressors already in service with compressor unloading means merely by substituting a valve plate provided with valve lifting mechanism for the standard 2,ese,24o

valve plate which does not have the valve lifting I mechanism.

A slight amount of clearance is provided be-,

tween the piston 64 and the passage'66 in which the piston slides so that upon closure of the valve 32 the high pressure gas may escape past the piston 64 into the passage 75 so as to equalize the pressure on the opposite sides of the piston 64. Upon equalization of the pressure on the opposite sides of the piston 64, the spring 68 causes the piston to assume a position in which the arms 12 do not interfere with the normal operation of the discharge valve ring 52.

While the form of embodiment of the invention said evaporator to said compressor, means for flowing a gas to be conditioned in thermal exchange relationship with said evaporator, means for flowing a cooling medium in thermal exchange with said condenser, said compressor comprising a plurality of outlet valves, means for holding one of said outlet valves open includin a valve lifting piston, means for subjecting one end of said piston to a pressure corresponding to the compressor discharge pressure, means for subjecting the other end of said piston to a pressure corresponding to the pressure within suction line, said last named means including a" passage leading from said suction line to the one end of said piston, a control valve in said passage, and means responsive to the temperature of said gas for controlling the opening and closing of said control valve, means for substantially equalicing the pressures on opposite sides of said piston, and means for normally biasing said pisto n into one extreme position when said pressures are substantially equalized.

2. Refrigerating apparatus comprising in combination, an evaporator, a condenser, a multiple cylinder compressor for withdrawing refrigerant vapor from said evaporator and for discharging compressed refrigerant into saidcondenser, said compressor having a plurality of discharge valves, means for holding one of said valves'open so as to reduce the capacity of said multiple cylinder compressor, said last named means utilizing the pressure of the compressed refrigerant for holding said one discharge valve open.

V 3. In combination, an evaporator, a condenser, a compressor, refrigerant fiowconnections between said evaporator, condenser and compressor including a suction line leading from said evaporator to said compressor, said compressor comprising an outlet port, a valve for said out let port, pressure operated means for holding said valve open, means for connecting said pressure operated means to said suction line, a solenoid valve controlling the flow in said connecting means, and a thermostat for controlling the operation of said solenoid valve.

4. Refrigerating apparatus comprising in combination, an evaporator, a condenser, a multiple cylinder compressor for withdrawing refrigerant vapor from said evaporator and for discharging compressed refrigerant into said condenser, said compressor having a plurality of discharge valves, means for holding one of said valves open so as to reduce the capacity of said multiple cylinder compressor.

5. Refrigerating apparatus comprising in combination, an evaporator, a condenser, a multiple cylinder compressor for withdrawing refrigerant vapor from said evaporator and for discharging compressed refrigerant into said condenser, said compressor having a plurality of discharge valves, valve lifting means for holdasaaaso ing one of said valves open so as to reduce the capacity of said multiple cylinder compressor, and means responsive to the temperature of a medium cooled by said evaporator for controlling said valve lifting means.

6. Mechanism for modulating the capacity of a multiple cylinder compressor by lifting one or more of the outlet valves of said compressor comprising in combination, a support, a piston slidably mounted in said support, means carried by said piston for lifting one of said outlet valves so as to render said outlet valve inoperative, means for subjecting one end of said piston to a pressure substantially corresponding to the discharge pressure of said compressor, means for subjecting the other end of said piston to a pressure lower than said discharge pressure, 4 means for substantially equalizing the pressures sure operated element having one portion subjected to a pressure substantially corresponding to the pressure within said head, means for subiecting another portion of said'pressure operated element to a diflerent pressure, said last named der means, a head for said cylinder means, a valve plate intermediate said head and cylinder, a valve carried by said plate, a valve lifting means carried by said plate including a pressure operated element having one portion subjected to a pressure substantially corresponding to the pressure within said head, means for subjecting another portion of said pressure operated element to a different pressure, said last named means including a fluid passage within said valve plate, and means for controlling the, flow of fluid-in said passage so as to control the operation of said valve lifting means.

9. Gas conditioning apparatus comprising in combination, an evaporator, a condenser, a compressor, refrigerant flow connections between said evaporator, condenser and compressor including a suction line leading from said evaporator to said compressor, means for flowing a gas to be conditioned in thermal exchange relationship with said evaporator, means for flowing a cooling medium in thermal exchange with said condenser, said compressor comprising a plurality of valves, means for holding one of said valves open including a valve lifting piston, means for subjecting one end of said piston to a pressure corresponding to the compressor discharge pressure, means for subjecting the other end of said piston to a pressure corresponding to the pressure within said suction line, said last named means including a passageleading from said suction line to the one end of said piston, a control valve in said passage, and means responsive tov the temperature of said gas for controlling the opening and closing of said control valve, means for substantially equalizing the pressures on opposite sides of said piston, and means iornormally biasing said piston into one extreme post-- means including a fluid paesage within said valve plate, and means for controlling the now of fluid in said passage so as to control the. operation I of said valve lifting means.

8. In, a multiple cylinder compresson, lintion when said pressures equal- 10. In a multiple der means, a head for said. cylinder means, a

valve plate intermediateeaid head and cylin der, a valve carried by said-plate, a valve on erating means carried by said plate and dis valve in a position so as one of said cylinders, and means-for the opera-,,

tion of said valve operatingmeans.

woman a cylinder compressor, cylm- 

